Art of coating metal articles



Patented Oct. 1, 1940 GFFE 2,216,376 ART OF COATING METAL ARTICLES Roy A. Rimmel, Pittsburgh, Pa, assignor to M. B.

Suydam Company, Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. Application July 15, 1939,

Serial No. 284,807

2 Claims.

This invention relates to improvements in the art of coating metal articles such as pipes, wire, bars, strips, sheets and the like, and contemplates 2. new coating composition and a new proc- 5 ess of coating metallic pieces or articles of the character specified.

In the manufacture of articles of this character, it is frequently desirable to provide the finished product with a protective coating to seal 10 the exposed metal surfaces against oxidation and moisture. Such a coating must completely envelope the article for protection during handling and storage, and in some instances serves as a base or under coating for finish coatings applied 15 by the ultimate user.

The present invention is especially applicable for use as a final step in the manufacture of certain coated metallic articles or pieces of the character above pointed out as such pieces come 20 from the mill or forming apparatus in a highly heated state; the latent heat of said products being utilized in the practice of my invention both in the deposition of the film producing ingre- 25 dients of an oil-in-water emulsion employed in the process as well as for effecting rapid evaporation of the water of the emulsion after application to the pieces.

In following my process, particularly in cases Where a desirable cool bath of emulsion is employed, the pieces to be coated are immersed while at a relatively high temperature into the bath, thus effecting a quenching action, whereby the temperature of the piece or pieces is reduced to a temperature such as will coact with the film forming ingredients of the bath to approximately simultaneously produce a thin uniform film coating on the immersed article, piece or pieces.

Hence; it will be seen that I have dispensed 0 with the necessity of reheating the articles or heating the emulsion, thus providing a considerable saving in time and expense in the manufacture of coated articles of the character herein contemplated.

In lieu of immersing or dipping the pieces in a. bath of emulsion a spraying operation may be followed.

The emulsion employed in the practiceof the present invention may be designated as adrying oil emulsion, containing in various proportions, a drying oil, soap, resinous ingredients or the like, in aqueous solution.

While such emulsions were known before my invention, I have found generally that they were not adaptable to the present coating process due to their inability to properly wet, apply or uniformly cover the surface of the heated article with the desired film, tending if deposited at all, to crawl and separate into a spotty porous discontinuous coating.

I have discovered that the afore-mentioned deficiencies in the emulsion may be overcome, and that the desired process of coating by quenching of the hot articles may be accomplished, by the addition of a wetting agent to the emulsion in proper proportion. I have found that by the addition of commercial triethanolamine to a drying oil and water emulsion, the desired coating is readily and uniformly deposited therefrom upon the hot articles. The physical results thereby attained are believed to be due to the added ability to completely wet the article and counteract the tendency of the heat to produce crawling of the deposited coating.

In the practice of my invention, the wetting agent or triethanolamine is preferably present with oleic acid, forming a soap, which, with the drying oil, provide the essential coating ingredients of the emulsion. In addition, I prefer to maintain the oll-in-wateremulsion as near neutral as possible, and hence may add a stabilizer such as tri-sodium phosphate to counteract any acidity present in the water used for the emulsion. Also, a defoaming agent such as octyl alcohol may be added for best performance of the emulsion.

The foregoing ingredients are combined in the usual manner and homogenized by mechanical means and heat to form a concentrated emulsion ready for commercial use by mixing with suitable quantities of water. I have found the following range of proportions to be suitable for the production of concentrated pipe and wire coating emulsions:

Parts by weight Raw or boiled linseed oil to 85 Oleic acid 8 to 12 Triethanolamine 1.8 to 4 Tri-sodium phosphate 3 to 6 Octyl alcohol 0. to 1 45 As an example 0f-a specific emulsion concentrate within the above range, for coating steel pipe, the following has been successfully employed:

Parts by weight To the foregoing emulsion concentrate, water is added in the proportion by weight of 1 to 12 parts of water to one part of the emulsion concentrate.

The said emulsion is prepared for my coating process as above described, and, when utilized as a bath of emulsion, is placed in a suitable container at substantially atmospheric temperature. Suitable circulation tanks or other means are preferably'provided for circulating the emulsion when in use so as to dissipate some of the heat of the articles being coated and maintain the emulsion bath at approximately room or atmos= pheric temperature, which temperature, in addition to being desirable for the coating operation, also serves to minimize the evaporation of the water content of the emulsion, thus reducing the necessity of frequently adding water to maintain uniform concentration of the bath.

The pipe, wire or other article to be coated is conveyed in any suitable manner to and immersed in the emulsion bath at a temperature of from about 200 F. to 600 F. The article is thereby quenched and reduced in temperature by the cooler bath and simultaneously enveloped by the emulsion coating, the article being immediately and completely wetted by the emulsion as hereinbefore described.

I have foundthat it is unnecessary for the article to undergo any prolonged soaking in the emulsion. On the contrary the article may be quickly withdrawn. While the quenching lowers the temperature of the article, a sufiicient quantity of heat remains to quickly evaporate the water of the emulsion, after the removal of the article from the bath.

Thus it will be seen, that my invention may readily be employed commercially asa final or finishing step in the manufacture of the articles specified, thereby utilizing the heat of the articles without loss of time and without the necessity of costly reheating, rehandling, etc.

In some instances it is desirable to employ a mechanical drag, as for example, a brushing or wiping device, against which the wire or the like is passed as it leaves the emulsion bath, whereby plated within the scope of the following claims.

I claim:

1. In an approximately continuous process of manufacturing coated metal articles of thagha'racter stated, the final step comprising quenching and completely wetting the heated article immediately following the formation of the article and while at a temperature of from about 200 F. to 600 F. in a substantially neutral bath maintained at substantially atmospheric temperature and containing an aqueous emulsion, having an oil phase, in parts by weight, of raw or boiled linseed oil to parts, oleic acid 8 to 12 parts, triethanolamine 1.8 to 4 parts, tri-sodium phosphate 3 to 6 parts and octyl alcohol 0.75 to 1 part, whereby to simultaneously reduce the temperature of the article and uniformly coat the article with the emulsion, and evaporating the water of the emulsion by the latent heat of the article to deposit thereon a developing protective coating.

2. In an approximately continuous process of manufacturing coated metal articles of the character stated, the final step comprising quenching and completely wetting the heated article immediately following the formation of the article and while at a temperature of from about 200 F. to 600 F. in a substantially neutral bath maintained at substantially atmospheric temperature and containing an aqueous emulsion having an oil phase, in parts by weight, of raw linseed oil 82.50 parts, oleic acid 9.38 parts, triethanolamine 1.80 parts, tri-sodium phosphate 3.00 parts and octyl alcohol 1.00 part, whereby to simultaneously reduce the temperature of the article and uniformly coat the article with the emulsion, and evaporating the water of the emulsion by the latent heat of the article to deposit thereon a developing protective coating.

ROY A. RIMMEL. 

